This invention relates to a voltage converter system of the same general type as disclosed in my U.S. Pat. No. 3,665,502. One of the embodiments disclosed in that patent comprises a motor-alternator set having a dc. motor energizable from a battery and having an alternator which produces an ac. voltage at its output. By connecting an ac. load device, such a tool with an induction motor, to the output of the converter, the load may be powered from the battery.
In many instances, such a motor-alternator converter is carried in a car or truck and is connected to the battery thereof so as to provide the user with mobile electrical energy for operating a power tool or the like at a location where utility electric service is unavailable. Generally speaking, a person who uses an ac. powered tool served by a vehicle-carried converter will connect the tool to the converter output with a relatively long three-wire extension cord having a ground wire for grounding the tool through the converter to the vehicle frame. To avoid needless drain on the battery, it is desirable to turn off the converter motor when the tool is not being operated. In the system disclosed in the aforementioned patent, the converter motor may be turned on and off at the working area so that the user need not walk back and forth between the working area and the converter each time it is desired to start or stop the motor.